The present invention relates generally to multicolor electrophotography apparatus such as a color copying machine and color printer, and more particularly to an arrangement for selective operations of developing devices provided around an electrostatic image holding device.
Various types of multicolor electrophotography apparatus have been developed heretofore, one known arrangement is disclosed in Japanese Patent Provisional Publication No. 60-250369 in which, after a formation of a latent image on an image holding device, a developing device selected in accordance with a required color approaches the image holding device and performs the developing process of the latent image in response to an application of a developing control signal, and after termination of the developing process, the selected developing device is separated therefrom with the application of the developing control signal being stopped. Generally, as techniques of separatively keeping the developing devices with respect to the image holding device in the non-developing state are known two methods, one being that the developing device is positioned to be in slightly separated relation to the image holding device and the other being that it is positioned to be in greatly separated relation thereto. However, an important problem in such a slightly separating method is to stably maintain the space therebetween because the unstable positioning of the developing devices causes deterioration of the image quality, thus resulting in requirement of a complex high-accurate mechanism and hence a high manufacturing cost. Furthermore, there is the possibility of irregularity of rotation of the image holding device due to load variations occurring in response to the operation of the developing device, resulting in deterioration of the image quality. On the other hand, any method that greatly separating the image holding device and the developer device causes the drive mechanism of the developing devices to be complex and results in a large space being required due to the great movement of the developing devices.